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Thursday, April 10, 2014

Three things I learned: rethinking flea control (or, HELP! there’s a biomass in my carpet!)

Fleas are the number 1 cause of pruritis (itchiness) in dogs and cats that I see in practice. By a mile.

Not sure if
you’re noticed, but fleas are going INSANE this month and they can be a
nightmare to control. One of the biggest challenges of managing fleas is managing
the expectations of owners – and maybe vets too.

Fleas caught when I bathed Phil and flea combed him. (He is on several reputable flea products - how can it happen? Read on).

ProfessorMichael Dryden, or Dr Flea as he is known in the business (not to be confused with Flea from the Red Hot Chilli Peppers), is a world expert on
fleas and has played a pivotal role in development of some of the more commonly
used antiparasiticides (say that with a mouth full of cereal). He presented a
webinar last week on flea biology which was entertaining. (The webinar was
hosted by MSD Animal Health, and it should be declared that MSD has just
launched a new flea product in Australia).

You would
think vets would get sick of continuing education on fleas, but actually they
are one of the commonest woes of our patients, causing everything from alopecia
(hair loss) to fulminant dermatitis to behavioural changes and lack of sleep
(for the owner and the animal). One of my goals in life is to fight fleas more effectively - but that ain't no humble goal.

Dr Flea's take on
fleas is a bit different to others I have heard. I often instruct owners to
treat their environment because fleas on the animal represent the tip of the
iceberg of infestation.

Dr Flea
says this: By the time a pet owner notices fleas, immature flea stages have
been developing in the home for the previous 1-2 months. (The fleas came from
pupae, which came from larvae, which came from eggs 1-2 months before).

The “biomass”
(what a creepy concept) of immature flea stages in the home environment will
continue to re-infest pets. Most of us are in denial about the biomass in our
carpet. And if the word biomass doesn't make you feel like Sigourney Weaver taking on aliens, I don't know what will. It elevates the battle against fleas to intergalatic warfare.

As pet owners we want the
infestation over yesterday (amen) but it isn’t biologically possible to
eliminate that biomass overnight. You can kill the fleas on your pet, but more young fleas
will emerge from this biomass, continuing to do so for 3-8 weeks, up to three
months in some homes. Up to 95 per cent of the biomass will develop and
complete its emergence within about two months.

If the
product you are using effectively prevents flea reproduction, you need around a
three month timeline (with variation between individual households due to
temperature and household conditions).

With the
release of decent spot-on treatments in the 1990s we moved away from blasting homes with chemicals to using products to break the flea life cycle, either
killing fleas before they reproduce on animals or directly inhibiting
reproduction.

The initial
speed of kill of any residual insecticide is directly proportion to its
concentration. The longer the product is on, the longer the speed of kill (the
residual speed of kill) – until eventually the speed of kill slows down enough
to allow fleas to lay viable eggs before they die (they only need 24-48 hours).

This is the
reproductive break point. The ideal product kills fleas before they lay eggs,
or actually destroys eggs.

Dr Flea
went into great detail about the way he performed flea studies, a methodology
he has refined over decades. So where do flea researchers go for their field
studies?

Tampa,Florida, it turns out. This is the flea capital of the US. Temperatures vary
from 27 to 35 degrees C with 75-85% humidity. Flea heaven. Some of the
infestations he described (>250 adult fleas visible on pets) made me wince.

Even Dr Flea said it isn’t ethical to use placebos in his studies because the
infestations in this area are life-threatening (heavily infested animals die
from anaemia or flea-borne infectious disease).

He looks
for fleas in an interesting manner. He combs certain areas – for example the
dorsal midline, base of the tail, lateral thorax on left and right and the
inguinal region. The number of fleas he sees in these areas represent 23 per
cent of the total adult flea burden on that animal (try this at home).

For those
of you who feel like fleas are worse than ever you might be on to something. Dr
Flea has observed a gradual steady increase in flea infestations since 1997. He
added that no flea product can kill every single flea before it can feed.

Veterinary Ethics: Navigating Tough Cases

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